As a cutting tool for use in a cutting process of a workpiece, such as metals, a cutting tool described in International Publication No. 2010/092807 (Patent Document 1) has been known. The cutting tool described in Patent Document 1 is used for a turn-milling process, such as a milling process, and is referred to as an end mill. The cutting tool for use in the turn-milling process includes a tool body (holder) that rotates around a rotation axis, and a cutting insert attached to an insert attachment seat (pocket) of the holder. The cutting tool described in Patent Document 1 further includes an upper wall part protruding against the pocket. Owing to the upper wall part, the holder is less apt to be warped, thus leading to enhanced rigidity.
When the rigidity of the holder is enhanced by making it difficult for the holder to be warped by simply disposing the upper wall part as in the holder described in Patent Document 1, the space of the pocket becomes narrow by an amount of the upper wall part. This may deteriorate chip discharge performance. The present embodiment aims at providing the holder capable of retaining good chip discharge performance while restraining occurrence of chatter vibration by having high rigidity.